Comb filter-based fiber-optic methane sensor system with mitigation of cross gas sensitivity

• Main Authors: Liu, Duan, Fu, Songnian, Tang, Ming, Shum, Perry Ping, Liu, Deming
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/96859; http://hdl.handle.net/10220/11652
• Institution: Nanyang Technological University

A remote fiber-optic methane gas sensor system is proposed and demonstrated with accurate gas concentration measurement and good mitigation of cross gas sensitivity. We use a polarization-maintaining photonic crystal fiber (PM-PCF)-based Sagnac loop filter to slice the spectrum of a broadband light source so as to precisely match several absorption lines of the methane gas within the near-infrared band. Meanwhile, a compact and cost-effective gas cell with multiple reflections is designed to enhance the interaction between the light beam and the methane gas to be detected, which also subsequently increase the system sensitivity. Due to the insensitive temperature dependence of the PM-PCF-based comb filter, we can obtain gas concentration measurement with a sensitivity of ~410 ppm. Moreover, by intentionally pumping the acetylene gas into the gas cell during the methane gas concentration measurement, the power variation caused by the interfering gas with 100% concentration is only equals to 0.7% of the power variation induced by the 100% concentration methane gas. Thus, effective mitigation of cross gas sensitivity is experimentally verified. The proposed fiber-optic methane gas sensor system is verified with low cost, compact size, potential capability of multipoint detection, and high sensitivity.